I do not recommend a dimmer for a blood python. Like has been said, they need constant temps and do not do well with a wide range of fluctuations, which is unfortunately the biggest fault with dimmers, cheap thermostats and rheostats.
Also, I would not trust a dimmer to handle flexwatt by itself, sounds like a ready made fire hazard. Dimmers are cheap and are best used when in conjunction with a thermostat. Meaning, dimmer plugged into the thermostat to ensure that when the dimmer malfunctions, it does not set your flexwatt on fire. The flexwatt will only get as warm as the thermostat is set.